Tube installation method

ABSTRACT

A method of installing a length of metal tube into a space which is accessible for insertion of the tube only by bending the tube to a radius which will buckle it, comprising flattening the tube between its ends to render the same flexible for bending or coiling for insertion into such space in generally straight form and subjecting the flattened tube in the space to internal fluid pressure to further straighten the same and to restore it to generally its initial cross section shape. Prior to the flattening operation the tube ends will be connected to appropriate fittings to maintain the tube ends of circular cross section and to facilitate the plugging of one end of the tube and the connection of a fluid pressure source to the other end of the tube.

United States Patent Green Mar. 7, 1972 [54] TUBE INSTALLATION METHOD Bichowsky ..l65/ 163 Fromaon et al. ..29/42l X Kraanitz ..29/421 ABSTRACT A method of installing a length of metal tube into a space which is accessible for insertion of the tube only by bending the tube to a radius which will buckle it, comprising flattening the tube between its ends to render the same flexible for bending or coiling for insertion into such space in generally straight form and subjecting the flattened tube in the space to internal fluid pressure to further straighten the same and to restore it to generally its initial cross section shape. Prior to the flattening operation the tube ends will be connected to appropriate fittings to maintain the tube ends of circular cross section and to facilitate the plugging of one end of the tube and the connection of a fluid pressure source to the other end of the tube.

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J/ /II T l// //f///////////// INVENTOR KELV/N D. GREEN I l l I l I /l I I/l/ Ill/l Ill/ll! ATTORNEYS TUBE INSTALLATION METHOD BACKGROUND OF THE INVENTION In connection with the inerting of aircraft fuel tanks or other long and narrow spaces it has been necessary to install large diameter thin wall tubing into such spaces, but, frequently such spaces are not accessible for longitudinal insertion of the tubing. If the tubing can be bent to a radius which will not buckle the same and which will permit insertion into such spaces, then, power means must be employed to straighten the inserted tubing. On the other hand, if the tubing cannot be inserted without buckling, then it has been the practice to successively insert and couple together short lengths of tubing, this being a time consuming and expensive operation.

SUMMARY OF THE INVENTION In the present tube installation method the tube with fittings assembled at the ends thereof is flattened between its ends to make the tubing nearly as flexible as a metal strip of double the wall thickness of thetube whereby the flattened tube may readily be fed in through an access opening leading into the space, or the length of tube may be coiled and taken into the space through the access opening and uncoiled by hand therein. When the flattened tube has thus been installed in the space, internal fluid pressure is applied through one end fitting while the other end fitting is closed as by a suitable cap or the like, the internal fluid pressure being effective to expand the flattened portion of the tube to generally its initial round shape. In addition, the internal pressure assists in further straightening of the tube if, in bending or coiling of the tube, the elastic limit has been exceeded.

As aforesaid, the present method also contemplates the installation of fittings at the ends of the tube before the flattening operation so that the tube ends will be retained circular in cross section and have fluidtight seals with the fittings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective view illustrating an elongated full span integral fuel tank constructed in the wing of an airplane into which it is desired to install a large diameter thin wall tube of length generally the same as the length of the tank;

FIG. 2 is a side elevation viewof a length of tube having fittings assembled at its ends and showing the tube as it is being flattened by passage between pinch rolls;

FIG. 3 is a cross section view of the flattened portion of the tube taken substantially along the line 33, FIG. 2;

FIG. 4 is a cross section view similar to FIG. 3 except that the flattening operation has left beaded edges to facilitate expansion of the tube by internal fluid pressure;

FIG. 5 illustrates a coiled length of tubing being uncoiled in the fuel tank illustrated in FIG. I; and

FIG. 6 illustrates the inserted tube after it has been subjected to internal fluid pressure to expand the same generally to its original round shape and to straighten the same.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 illustrates an elongated aircraft fuel tank 1 which is built into an aircraft wing 2, the tank 1 having an access opening 3 which will be closed by a suitable door or cover plate (not shown). If it be desired to install a large diameter, thin wall tube 4 to extend lengthwise in the tank I, the tube 4 would buckle if it were attempted to install the same from the access opening 3. Furthermore, even if the tube 4 could be installed irito the tank 1 through the opening 3 by curving the same to a relatively large radius, the inserted tube 4 could not be thereafter straightened by hand, whereby some type of power straightener would have to be employed to straighten the inserted curved tube 4. Moreover, the initial bending of the tube 4 may require use of a tube bender.

To make possible the installation of a long tube 4 laterally into a long narrow space without buckling or without requiring successive insertion and coupling together of short lengths of tube, it is contemplated in the present invention ti) install suitable fittings 5 and 6 at the ends of the tube 4 and to substantially flatten the tube 4 between the fittings 5 and 6 as by passing the tube 4 between suitable pinch rolls 7 as shown in FIG. 2. Accordingly, the tube 4 is thereby flattened as shown in FIGS. 2 and 3 (or as shown in FIG. 4 to provide beaded edges), and therefore, the flattened portion 8 of the tube which may be of say, 30-foot length, would have nearly the flexibility of a 30-foot-long metal strip of width about one and one-half times the diameter of the tube 4 and of thickness about twice the tube wall thickness. Thus the flattened tube 4 could readily be snaked into the tank I through the access opening 3 or the flattened tube 4 may be coiled as in FIG. 5 to form a coil 10 which is inserted through the access opening 3 into the tank I and there uncoiled by hand to cause the leading end with fitting 5 to move toward the other end of the tank 1.

If there is another access opening at, the other end of the tank 1 a spring metal electrician's snake may be inserted through such other opening and connected to the leading tube fitting 5, whereby the coiled tubingin the tank 1 or the tube 4 outside the tank 1 may be pulled in and through the tank I and through the openings in the wing spars which may be provided in an integrated wing tank construction as illustrated herein.

Preferably, before the leading end of the tube 4 is inserted through the access opening 3 a closure cap 9 may be secured to the fitting 5 to close it. After the tube 4 has been inserted and generally straightened by hand during the uncoiling operation, a source of fluid under pressure is connected to the end fitting 6 to effect further straightening of the inserted tube 4 and to expand the tube 4 to generally its original round shape as shown in FIG. 6.

As an example of the present invention a 30-foot length of thin wall tube 4 may, after flattening, be hand formed into a plural turn coil 10 of from, say, 14 to 18 inch diameter which can readily be inserted into the tank 1 or other close quarters even through a rectangular access opening 3 of flattened tube width by l4 to 18 inch length. The coil 10 may easily be uncoiled by hand to insert the 30-foot length of tube 4 into along narrow space such as the fuel tank 1 herein illustrated by way of example. The tube 4 may be of stainless steel, aluminum alloy, or other suitable material. If desired, the straight length of flattened tube 4 (FIG. 2) may be inserted through the access opening 3 into the space and fed in like an electricians or plumbers snake or the coil 10 may be disposed outside the tank 1 and uncoiled as it fed in through opening 3 to cause the leading end to move longitudinally of the space.

I claim:

1. The method of installing a length of tube into a space which is accessible for insertion of the tube only by bending the tube to a radius which would cause buckling thereof, said method comprising the steps of flattening a length of tube between the ends thereof; bending the flattened tube to a radius permitting insertion of at least one end portion into such space; progressively straightening the flattened and bent tube from such ohe end portion to the other end portion as it is advanced longitudinally in such space, and admitting fluid under pressure into the inserted tube of magnitude to restore the tube to generally its original cross section shape.

2. The method of claim I wherein tube fittings are assembled on the end portions of the tube prior to flattening of the tube so as to maintain the end portions of the tube in original shape.

3. The method of claim 2 wherein the fitting at such one end portion of the inserted tube is closed so that fluid under pressure may be applied through the fitting at such other end portion of the inserted tube.

4. The method of claim I wherein the tube after having been flattened is bent to spirally coiled form for straightening by uncoiling thereof and longitudinal feeding into such space.

5. The method of claim 1' wherein the tube after having been flattened is bent to flat spirally coiled form for insertion of the coil into such space for straightening by uncoiling thereof and longitudinally feeding in such space. 

1. The method of installing a length of tube into a space which is accessible for insertion of the tube only by bending the tube to a radius which would cause buckling thereof, said method comprising the steps of flattening a length of tube between the ends thereof; bending the flattened tube to a radius permitting insertion of at least one end portion into such space; progressively straightening the flattened and bent tube from such one end portion to the other end portion as it is advanced longitudinally in such space; and admitting fluid under pressure into the inserted tube of magnitude to restore the tube to generally its original cross section shape.
 2. The method of claim 1 wherein tube fittings are assembled on the end portions of the tube prior to flattening of the tube so as to maintain the end portions of the tube in original shape.
 3. The method of claim 2 wherein the fitting at such one end portion of the inserted tube is closed so that fluid under pressure may be applied through the fitting at such other end portion of the inserted tube.
 4. The method of claim 1 wherein the tube after having been flattened is bent to spirally coiled form for straightening by uncoiling thereof and longitudinal feeding into such space.
 5. The method of claim 1 wherein the tube after having been flattened is bent to flat spirally coiled form for insertion of the coil into such space for straightening by uncoiling thereof and longitudinally feeding in such space. 